Sounds like you have a pretty darn good room, so thats a plus.
The salesman was misleading you slightly. The Mackie preamps are a bit smeared and dark, so he's not exactly wrong about curing some digital "coldness" or "harshness"
but its the way in which the Mackie is doing it. You could put a blanket over your mic, and that would darken the sound too.
But you're gonna miss alot of things
you DO want in the sound when you do that.
I think your setup sounds very decent. However, it is fairly outdated. Dont get me wrong here, im not meaning to insult you or your setup. You could get
some very good results with it.
However, you could probably get a much higher fidelity sound from something like the Sony D-50 handheld recorder. The analog to digital converters in the Sony are
most likely far superior to the Tascam. The resolution is certainly more than double the Tascam as well. 24 bit/ 96khz. I have a friend who owns the Sony and it sounds AMAZING.
The Sony would also simplify your whole process and would be a huge downsizing. No more cables, mixers, multiple mic stands, etc etc... Just the D-50 on a single mic stand, and you're ready to go. When you're done, you fly it into your computer.
If you're e - b a y savy, you could get just enough cash for your gear to get hold of the Sony. I would hold on to your Marshall mics though. But the Tascam, and the Mackie, are easily replaced and then some, by the Sony.
I have been recording for a long time via outboard preamps, soundcards, condensor mics, etc...
But i have to admit, after hearing the Sony, im starting to think about changing the way i record classical guitar.